Outstanding dark orange crystals of the very rare mineral siudaite (IMA 2017-092) from the type and only known locality worlwide in Khibiny: Eveslogchorr Mountain, Khibiny Massif, Murmansk Oblast, Russian Federation. — Photo: David Hospital · CC BY-SA 4.0
Siudaite
Siudaite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₈(Mn²⁺₂Na)Ca₆Fe³⁺₃Zr₃NbSi₂₅O₇₄(OH)₂Cl·5H₂O.
It crystallizes in the hexagonal crystal system (space group R3m). It is a member of the Eudialyte structural group.
Key properties: Mohs hardness 4.5; specific gravity 2.96; White streak; Vitreous luster; optically uniaxial.
IMA symbol Siu, IMA status: approved, named in 2018.
A product of the hydrothermal alteration of a primary eudialyte-group mineral presumably related to georgbarsanovite, in a peralkaline pegmatite.
It is found associated with Aegirine, albite, microcline, nepheline, astrophyllite, loparite-(Ce).
The mineral was named to honor the Polish mineralogist and geochemist Rafał Siuda (b. 1975), a specialist in the mineralogy and geochemistry of supergene zones of the ore deposits of Lower Silesia.